EF核心插入多对多表

Question

我用Razor Pages搭建了User模型，在创建页面上我想在联结表UserRoles上插入用户角色。

这是我的模特

[Table("Users")]
public class User
{
    public User()
    {
        IsActivo = true;          
    }

    public int Id { get; set; }

    [Required]
    [Display(Prompt = "Username")]
    public string Username { get; set; }
    [Display(Name = "Último Acesso")]
    public DateTime? DataSessao { get; set; }
    [Display(Name = "Activo")]
    public bool IsActivo { get; set; } 
    public Colaborador Colaborador { get; set; }

    public ICollection<UserRoles> UserRoles { get; set; }
}

这是创建模型

public class CreateModel : PageModel
{
    private readonly HutIS.Models.HutISContext _context;

    public CreateModel(HutISContext context)
    {
        _context = context;
    }

    public IActionResult OnGet()
    {
        DepartamentosOptions = _context.Departamento.Select(d =>
              new SelectListItem
                  {
                       Value = d.Id.ToString(),
                       Text = d.Nome
                  }).ToList();


        RolesOptions = _context.Roles.Select(d =>
                  new SelectListItem
                      {
                         Value = d.Id.ToString(),
                         Text = d.Type
                       }).ToList();

        return Page();
    }

    [BindProperty]
    public User User { get; set; }
    public List<SelectListItem> DepartamentosOptions { get; set; }
    public List<SelectListItem> RolesOptions { get; set; }

    public async Task<IActionResult> OnPostAsync()
    {
        if (!ModelState.IsValid)
        {
            return Page();
        }

        _context.User.Add(User);

        await _context.SaveChangesAsync();

        return RedirectToPage("./Index");
    }
}

在html上

<div class="form-group">
    <label asp-for="User.UserRoles" class="control-label"></label>
    <select asp-for="User.UserRoles" asp-items="Model.RolesOptions" class="form-control form-control-sm">
        <option value="">Selecione um Departamento...</option>
    </select>
    <span asp-validation-for="User.UserRoles" class="text-danger"></span>
</div>

我不确定我该怎么做，当然我会在这里遇到异常，但是如果UserRoles是User中的一个集合，该如何绑定UserRoles呢？

编辑

我解决了异常问题，它与模型属性有关。 现在的问题是，没有在UserRoles表上插入任何内容，我不太确定该怎么做，因为与部门相比，User的UserRoles没有导航属性。

如您所见，关系是正确的

Answer 1

对于<select multiple="multiple" asp-for="User.RoleIds" asp-items="Model.RolesOptions" class="form-control form-control-sm"> ，它将提交RoleId值而不是Role Object ，则需要定义public ICollection<int> UserRoleIds { get; set; } public ICollection<int> UserRoleIds { get; set; } public ICollection<int> UserRoleIds { get; set; }接受RoleIds。

请按照以下步骤操作：

1. 使用UserRoleIds定义ViewModel

    public class UserVM { public UserVM() { IsActivo = true; } public int Id { get; set; } [Required] [Display(Prompt = "Username")] public string Username { get; set; } [Display(Name = "Último Acesso")] public DateTime? DataSessao { get; set; } [Display(Name = "Activo")] public bool IsActivo { get; set; } public ICollection<int> RoleIds { get; set; } } 

2. 剃刀型号

    public class CreateModel : PageModel { private readonly TestRazorContext _context; public CreateModel(TestRazorContext context) { _context = context; } public IActionResult OnGet() { RolesOptions = _context.Role.Select(d => new SelectListItem { Value = d.Id.ToString(), Text = d.Type }).ToList(); return Page(); } [BindProperty] public UserVM User { get; set; } public List<SelectListItem> RolesOptions { get; set; } public async Task<IActionResult> OnPostAsync() { if (!ModelState.IsValid) { return Page(); } //create user var user = new User { Username = User.Username, //rest properties }; _context.User.Add(user); await _context.SaveChangesAsync(); //set user role var userRoles = new List<UserRoles>(); foreach (var roleId in User.RoleIds) { userRoles.Add(new UserRoles { UserId = user.Id, RoleId = roleId }); } _context.UserRole.AddRange(userRoles); await _context.SaveChangesAsync(); return RedirectToPage("./Index"); } } 

3. 剃刀视图

    <form method="post"> <div class="form-group"> <label asp-for="User.Username" class="control-label"></label> <input asp-for="User.Username" /> </div> <div class="form-group"> <label asp-for="User.RoleIds" class="control-label"></label> <select multiple="multiple" asp-for="User.RoleIds" asp-items="Model.RolesOptions" class="form-control form-control-sm"> <option value="">Selecione um Departamento...</option> </select> <span asp-validation-for="User.RoleIds" class="text-danger"></span> </div> <input type="submit" value="Submit"/> </form>